Exported files are low resolution

[Mjj18]

I need a Min resolution of 897 x 1497 pixels (300DPI). I made my drawing on a 11 x 8.5 inch document (standard page size). Whether I export in png, bmp, tiff... they all come out as 816x1056. I then monkeyed with the PNG export option. Its default appears to be 96 pixels/inch, I've cranked that up to 300 but then the width and height shrink, so I changed those back to 11 x 8.5. The resolution then comes out as 2554 x 3305 but only 718KB. Far less than the 2.46MB I get with bmp (but wrong resolution). I don't know if file size means much here but it seems common that the smaller the file size the worse quality. I'm uploading my work to a website for custom card printing and I want to be sure they are getting the best possible images. I've also went into Tools_Options_Print and checked Reduce bitmaps and chose resolution of 300DPI. Hasn't helped. I know I'm not printing but exporting but I thought, who knows, maybe it would have an effect.

[acknak]

I'm not seeing a problem, other than I have to do the arithmetic myself: I can't change the export resolution to 300 dpi and have the height/width calculated automatically; I have to figure out the pixel height or width and enter that myself.

I am seeing a problem exporting a full letter-size page at 300 dpi. The image size is ok (2550 x 3300) but parts of the page at the right and bottom are missing in the exported image. This may be a result of some internal limit.

[Mjj18]

I'm not sure what your response is saying. 300 dpi on a regular size page shouldn't be a problem.

[acknak]

Shouldn't be a problem, but it is.

[John_Ha]

I don't know if file size means much here but it seems common that the smaller the file size the worse quality.

That is a complete overgeneralisation and absolutely wrong in this case!

The file size for any given image is a function of the type of image (photo? graphic?), how complex the image is (blocks of identical colour? blocks of similar colour? text? edges? number of colours? colour depth?), and what type of compression is used (PNG (up to 16 million colours, 24 bit), GIF (only up to 256 colours, 8 bit), JPG etc, or no compression with BMP).

See [Tutorial] Some useful hints on using images for a discussion on images in Writer and applicable to Draw.

BMP files do not use compression so a 500 x 400 pixel BMP file has 500 x 400 = 200,000 pixels where each pixel is defined by three bytes. The data therefore saves as 600,000 bytes. It actually stores as 600,054 Bytes as there are 54 Bytes of metadata saying it is a BMP file and the image is 500 x 400 etc.

Red is defined as [255, 0, 0] so a BMP file has 600,000 identical entries of [255, 0, 0], which is written in Hex as FF0000, so a BMP file has some metadata followed by 600,000 x FF0000 as
"metadataFF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000 ... FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000FF0000". Note that if every pixel was different colour, the BMP file would still be the same size.

PNG files use lossless compression, so if you save a graphic (not a photo) as a PNG file it will be smaller, and much, much smaller if the image does not have much detail. See the uploaded red.PNG file - it is a 500 x 400 pixel image, with all red pixels, and it saves as a PNG file with only 1,470 Bytes which includes the metadata. Effectively the PNG files stores only "500 pixels wide, 400 pixels deep, every pixel is [255, 0, 0]". As you can see that took only 60 characters to write, which is 60 Bytes, yet it defines the image perfectly! Note that if every pixel was different, the PNG file would now be much bigger.

If this solves the problem, please click the Edit button on your original post and add [Solved] in front of your subject.

[lockerdog]

I think I had the same problem as the original poster.

I think there may be a way to make this work--at least it seemed to work for me.

When exporting PNG (which is what I'm doing) there are options both to change resolution (i.e. DPI) and options to change the size. I changed the resolution and *then* changed the size, in that order, and it worked for me (I was able to get high resolution PNG files exported).

When I tried to keep the original size and then change the resolution, it always reverted to exporting something with low resolution. When I tried to change the original size and then change the resolution, changing the resolution value always made the size parameters drop to a very small size and then the exported file was of low resolution. So I'm not sure why this was happening (and it sounds like you might have had the exact same problem, yes?) but I think it might work for you if you change the resolution and then change the size in that order.

John, a pious Noahide
(running Open Office Writer 4.1.7 and Windows 7 Home Premium 64-bit)